Contract Electronics Manufacturing and PCB Assembly Blog

PC Board Assembly: All About Perfect Tolerances

Posted by Laura Austin on Sat, Mar 23, 2013 @ 07:00 AM

Without the help of rigorous testing and assembly compliances, the whole process of PC Board assembly wouldn't be able to endure the life cycle of being a PCB and more than likely would fail much sooner than later. All of those tests aren't just for the sake of testing, they are implemented to make sure that everything is in working order and the board itself can withstand extreme heat, cold, and even weight distribution and tolerances. However, the PCB-assemblytests themselves even need to have perfect ratings--especially when it comes to tolerances, in particular.Tolerances are what the PCB will go through in order to pass all of its testing, making sure it can work properly in certain situations without short circuiting, breaking, or shutting down completely. But most importantly, there are also tolerances during the design phase to make sure that the board is "balanced" when it comes to all of its components and won't suffer from breakage or overload.

Designing The Board
When you're ready to start making blueprints of the next design of your board, you probably already have something in mind when it comes to what it should do, how it needs to be done, and placement of the wiring and other parts for the best use of the surface area. The same thing is happening with the manufacturer during the PC Board assembly, too. What do the designers look for exactly for the perfect tolerance?

  • Thickness of the whole board. It can't be too thick or too thin, but just right.

  • Tolerances of the aspect ratio. During the PC Board assembly, aspect ratio is the thickness of the entire board that is divided by the diameter of any drilled holes in the board.

  • Actual hole size. When drilling holes into the board, even the holes themselves need to have a certain diameter, length, and width.

  • Pad size and annular ring. This is the copper plating and radius of the entire pad, respectively. Both of them can depend on size, since it relies on your specs and the math involved.

  • "Trace and Space," or copper tracing and spacing. There needs to some air gaps between any copper components or features.

These are only a few of the aspects of the PCB design and manufacture and engineers need to account in their tolerances, as it entirely depends on the project itself. When consulting with the manufacturer, all of this will PC-board-assemblybe brought up and mapped out so that the tolerances can be perfectly balanced and the PCB itself the highest quality.

Assembling The Board

Once everything has been plotted out in the design process, it is time to put everything together and follow the tolerances sheet. Once everything has been designed and assembled, it goes through all of its testing and compliance reports to make sure everything is where it needs to be and won't malfunction or break.

As a note, it is also during this time that tolerances are given extra "clearance" normally when it comes to air gaps, drilling holes, slot width, and the copper features because the machinery sometimes used during the assembly process will need more room to have the best precision. Also, drill bits might "wander" and need the extra room.

This doesn't mean that the board will be of lesser quality, however. It will still be a high quality manufactured product, but these sorts of measurements need to be considered for the best tolerances. All of this can be consulted with your manufacturer about the manufacturing services beforehand, and they can walk you through the entire process so you can know exactly what's happening with your project.

Topics: pcb assembly service, pcb assembly, pc board assembly, PCB assembly technology, PB board assembly manufacturer

PCB Assembly Service: Advantages Start With Economies of Scale

Posted by Laura Austin on Sat, Dec 01, 2012 @ 07:00 AM

When it comes to your operating budget, one of the biggest things you're probably concerned about is the manufacturing and distribution Printed Circuit Boards (PCBs) that are being assembled specifically for you. 

However, being able to handle larger orders normally means being able to ramp up your efforts and being able to expand your services. Of course, getting to that point can take some PCB-assembly-servicetime, but when you do expand your economies of scale, then it's probably time to find a PCB assembly service which can handle all of that extra work.

There are all kinds of assembling operations for you to utilize out there, and you don't even have to ship the work overseas to China or other labor-intensive countries for the sake of better prices. In fact, you can keep everything within the United States without having to go way over budget. You get to retain all of that quality assembly of your PCBs, too. But, what are the exact advantages of building up your assembly efforts?

More For Your ROI

All businesses and all industries have a Return On Investment, some of them easier to obtain than others. When you start producing more, it usually means a higher curve for ROI, but PCB assembly fortunately can return all of that investment back immediately and tenfold.

More Equals Less

It's well known saying with some facts even backing it up. Being able to assemble and distribute more PCBs means it will cost less for you in the long run, as the PCB assembly service will obtain wholesale prices on components and have a better utilization of overhead.

You don't have to worry about budgeting (well, won't have to worry as much) in component
prices into your assembly prices when you're bulking up orders. Be able to take most of the guess work out of components and budgeting, let the PCB assembly service handle that and allow you to continue to run your business.

Keeping It All At Home

Like mentioned previously, your PCB assembly service doesn't have to be an overseas operation that you rarely (if at all) get to have direct contact with. You can keep everything on shore in the United States with an entirely U.S. based assembly service, not one with engineers in the U.S. ordering parts from off shore factories.

Speaking of, keeping your assembly team within the United States also means running a much lower risk of dealing with counterfeit and faulty components, which can result in thousands of dollars down the drain if the entire batch ends up being bad. Keep your entire service all at "home" and you won't regret it.

Faster, Reliable ResultsPCB-assembly

Taking the manufacturing from in-house to a PCB assembly service might seem like a hassle at first, but it can mean your business can focus on being a business while highly trained engineers and assemblers take care of your PCBs, from design all the way to testing and putting the final product into your hands. 

All of the man hours spent on ensuring the quality of the components can be allotted to a product assembly service which does this for a living, while you can use that extra time on business development, marketing, acquiring more customers, and much more.

There are so many other positives to having a reliable, U.S.-based PCB assembly service help you grow, these just so happen to be the most popular reasons. Have you considered taking the time to look into assembly services? What entices you the most?

Topics: pcb assembly service, pcb assembly, PCB, PCB assembly technology

Tin Whisker Formation and Impact on PCB Assembly Reliability

Posted by Laura Austin on Sat, Oct 20, 2012 @ 07:00 AM

Considerably different from dendrites or other such shapes in components, tin whiskers can pose a very serious problem for a circuit board and other types of technology if they happen to be found and identified correctly. Tin whiskers are structures of "crystalline" formations that resemble whiskers and are most commonly found in electroplated tin that is used a finish on components, including PCB.

Several different components of PC Board assembly utilize tin for coating, although some measures were made to prevent tin whiskers from forming. One way is to reintroduce lead into the market, which can help stabilize the finish, however the exposure to lead over a long PCB Assembly Componentsperiod of time is still dangerous and most governments still ban its use. Because of this, most companies used special alloys.

Also, some industries are still allowed to use lead in their PCB assembly of technology components and there can be other ways to prevent tin whiskers without it that you can implement. But first, what are other ways these whiskers can form?

  • Stresses from poorly formed components which do not fit well together.

  • The use of intermetallic formation can also cause tin whiskers.

  • Many different outside sources of stress can create tin whiskers to form, which means the entire area of the components need to be checked.

  • Bending, stretching, or scratches from both external and internal problems are another big factor to consider when looking for tin whiskers.

Assembly is at most risk, which automatically means a faulty product if the whiskers begin to grow and interfere with the components. While tin whiskers may seem harmless enough, they pose a very real threat to the product as well as people. One of the most common problems from whiskers in PCB assembly is a short circuit or arcing. Electrical equipment can suffer shortages and even harm people from their arcing, which ultimately means lost time and money.

This impact on global PCB assembly means broken equipment, ruined circuity, and shoddy craftsmanship overall that needs to be addressed. In order to prevent or mitigate tin whisker formation, you can take these precautions:

  • If at all possible, remember to avoid the use of pure tin plated coating and other equipment. Most companies utilize alloys to help stabilize the components to mitigate tin whiskers, but caution still needs to be advised.PCB Assembly

  • Simply replate the areas that are at high risk of whiskers by either outsourcing to a contract manufacturing company or attempting it in-house. However, it is highly advised that you use an outside manufacturer to help strip down the current plating and put on a newer plating to avoid tin whiskers.

  • A foam encapsulating coat or housing can be applied to whisker prone areas, helping prevent any problems in the future. However, it entirely depends on the type of foam encapsulating coat used, how much of it is applied, and how dangerous the whisker prone area is. Fortunately, however, this normally helps prevent short circuits in most cases.

  • Alternatively, you can try to relieve any stress to the area with a hot oil reflow or new soldering job.

Working with a reliable assembly manufacturer who is willing to help with any tin whisker problems is also a very highly recommended route. Most are certified to make sure that no pure tin components are used whatsoever and instead alloys are used to mitigate whisker formation. There is always the risk of faulty and counterfeit parts which could also cause tin whiskers, but working with US-based companies normally means a higher standard of quality overall.

Remember, tin whiskers are much different than dendrites and cause serious damage to circuity! Simply ignoring the issue can result in failures in the components with short circuiting and arcing.

Have you ever experienced tin whiskers in your PCB components? What mitigation measures were put in place?

Topics: electronic manufacturing company, pcb assembly service, pcb assembly, Contract Electronic Assembly, electronic PCB assembly, contract electronics manufacturing, assembly manufacturer, PCB assembly technology, electronics assembly companies, US manufactured electronics